1. Field of the Invention
The present invention relates to a cutting blade, and in particular, to a method and an apparatus for manufacturing high speed cutting blades used for cutting stones, metal, concrete, asphalt, bricks, earthen pipes, etc., and a cutting blade manufactured by the same.
2. Description of the Related Art
In a building site or a civil engineering site, cutting blades of a disk shape are generally used as cutting tools for cutting stones, metal, concrete, asphalt, bricks, earthen pipes, etc. Each of those cutting blades comprises a disk-shaped steel core with a predetermined thickness made of a high speed tool steel such as carbon tool steel, low carbon tool steel or the like, and a plurality of cutting segments made of a diamond-metal powder mixture, usually, by mixing diamond particles and metal powder of a specific ingredient, forming the mixture into a predetermined shape and sintering the same at a high temperature. The cutting segments are fixedly attached to the periphery of the disk-shaped steel core at regular intervals, usually by welding.
As shown in FIG. 1, the conventional method for manufacturing those cutting blades mainly comprises the steps of: preparing a diamond-metal powder mixture by mixing diamond particles having a predetermined size with metal powder having a predetermined ingredient and size; forming the diamond-metal powder mixture into cutting segments of a predetermined shape by pressing the mixture in a forming pattern of a forming die using pressurized punching means; sintering the formed cutting segments in a separate sintering furnace; and welding the sintered cutting segments to the periphery of the disk-shaped steel core at regular intervals using a separate welding apparatus. Each manufacturing step of the conventional method is independently performed in a separate station, respectively.
In addition, before welding the sintered cutting segments to the periphery of the steel core, the conventional method for manufacturing the cutting blades further comprises the steps of: barrel-finishing to remove burrs or flashes undesirably formed at the peripheral edges of the cutting segments in the forming step; and radius grinding to conform the inner curvature of the sintered cutting segments to the outer curvature of the periphery of the steel core to which those cutting segments are to be welded.
In general, upon completion of the manufacturing process by completely welding the cutting segments throughout the periphery of the disk-shaped steel core at regular intervals, further steps of dressing the surfaces of the cutting segments, and painting or marking on the surface of the cutting blade may optionally be performed.
According to the conventional method, each step of manufacturing is independently performed using separate apparatus, equipments or devices, such as forming die, sintering furnace, barrel-finishing machine, radius grinder, and welding machine, which are separately installed in different places.
FIG. 2 schematically illustrates a typical forming die for forming the cutting segments in a conventional apparatus for manufacturing the cutting blades. Referring to FIG. 2, in general, the forming die comprises: an upper press having an upper punch assembly 11 consisting of a plurality of vertically reciprocating punches 12; a lower press having a lower punch assembly 13 consisting of a plurality of vertically reciprocating punches 14; and a die assembly 18 having forming patterns 15 of a cross-sectional shape corresponding to that of the punches of the upper and lower presses. On the upper surface of the die assembly 18, forming material filling feeders 16 are placed at left and right sides, respectively, so as to be movable in horizontal direction by hydraulic cylinders 17. The forming material filling feeders 16 are connected to separate powder material supplying sources (not shown).
In addition to the forming die as described above, the conventional apparatus for manufacturing the cutting blades also comprises a sintering furnace, a barrel-finishing machine, a radius grinder, a welding machine and so on, which are separately installed in different places and perform independent functions. All of them are commercially available in the field of the present invention and therefore no drawings and detailed description will be provided herein.
In manufacturing cutting blades according to the conventional method and the conventional apparatus, first, diamond-metal powder mixture is prepared by mixing diamond particles of a predetermined size and metal powder of a predetermined ingredient and size. The diamond-metal powder mixture is filled into the forming patterns 15 of the die assembly 18 of the forming die by the forming material filling feeders 16 horizontally reciprocating on the upper surface of the die assembly 18, and then formed into cutting segments of a predetermined shape by pressing the mixture in the forming pattern 15 with the vertically reciprocating punches 12 by moving down the upper punch assembly 11 of the upper press. At this time, the vertically reciprocating punches 14 of the lower punch assembly 13 of the lower press are maintained in a stationary state at a desired position.
Moving upwardly the upper punch assembly 11 apart from the forming pattern 15, and then moving upwardly the lower punch assembly 13 with a predetermined distance, the cutting segments formed as described above are released out of the forming pattern 15 by the upwardly moving punches 14 of the lower punch assembly. The formed and released cutting segments are then moved to a sintering station from the forming die, and put into a separately installed sintering furnace (not shown) and sintered under a predetermined temperature for a predetermined time period. The sintered cutting segments are then moved to a welding station and welded to the periphery of the disk-shaped steel core at regular intervals using a separate welding machine (not shown).
However, prior to welding the sintered cutting segments to the periphery of the disk-shaped steel core, it is necessary to perform barrel-finishing in a separate station so as to remove burrs or flashes undesirably formed at the peripheral edges of the cutting segments in the forming step, and radius grinding in a separate station so as to conform the inner curvature of the sintered cutting segments to the outer curvature of the periphery of the steel core to which those cutting segments are to be welded.
In the conventional method for manufacturing the cutting blades, as described above, the step of forming the cutting segments of a predetermined shape by pressing the diamond-metal powder mixture, the step of sintering the formed cutting segments, and the step of welding the sintered cutting segments to the periphery of the disk-shaped steel core are independently performed in separate stations. Furthermore, prior to welding the sintered cutting segments to the periphery of the disk-shaped steel core, the step of barrel-finishing to remove the burrs or flashes formed at the peripheral edges of the cutting segments in the forming step, and the step of radius grinding to conform the inner curvature of the sintered cutting segments to the outer curvature of the periphery of the steel core should also be independently performed in separate places. Therefore, the conventional method requires to move half-finished or intermediate products in every step of manufacturing and to perform all the steps of manufacturing at separate stations using separate apparatus, equipments or devices, and as a result, the conventional method not only consumes a long period of time for manufacturing but also incurs a considerable amount of loss in materials, energy and manpower.
The conventional manufacturing apparatus also requires, in every step of manufacturing, to use separate apparatus, equipments or devices separately installed in different stations, which results in requiring a large space or separated places to install the entire set of manufacturing apparatus, and which, throughout the entire steps of manufacturing, causes not only a troublesome to move the half-finished of intermediate products to each station but also a considerable amount of loss in materials, energy, manpower and so on.
FIG. 3 is a partial sectional view illustrating a structure of the cutting segments in a conventional cutting blade. FIG. 4 is a partially enlarged sectional view illustrating an example that the surfaces of cutting segments have been abraded during a cutting operation of the conventional cutting blade.
The conventional cutting blade is manufactured, as described above, by mixing diamond particles having a predetermined size with metal powder having a predetermined ingredient and size, forming the diamond-metal powder mixture into cutting segments of a predetermined shape by pressing the mixture in a forming pattern, sintering the formed cutting segments in a sintering furnace, and welding the sintered cutting segments to the periphery of a disk-shaped steel core.
In a cutting process, a plurality of cutting segments attached to the periphery of a cutting blade rotating at a high speed comes in contact with an object to be cut, and the object is cut by mainly a strong cutting force of the diamond particles contained in the cutting segments. In order to enhance the cutting efficiency and life cycle of the cutting blade, therefore, it is preferable to uniformly distribute the diamond particles in the cutting segments made of a diamond-metal powder mixture. Also, after using the cutting blade for a long period of time, the surfaces of the cutting segments contacting with the cutting objects is gradually abraded, and as a consequence, the diamond particles contained in the cutting segments are exposed outside. It is, therefore, preferable to maintain the diamond particles not to be fallen off from the cutting segments as long as possible.
In the conventional cutting blades, however, it is difficult to uniformly distribute the diamond particles as desired when mixing the diamond particles with the metal powder. As a result, distribution of the diamond particles in the cutting segments formed and sintered in the subsequent steps of manufacturing becomes non-uniform. Further, after using the cutting blade for a long period of time, the cutting segments become abraded and, as a result, the exposed diamond particles are easily fallen off from the cutting segments.
As shown in FIG. 3, the conventional cutting blade 20 has non-uniformly distributed diamond particles 23 and metal powder 24 in the sintered diamond-metal powder mixture of cutting segments 22 welded to the periphery of a disk-shaped steel core 21. Therefore, after using the cutting blade for a long period of time, the surfaces of the cutting segments 22 become non-uniformly abraded, thereby deteriorating the cutting efficiency and life cycle of the cutting blade.
Further, the sintered metal powder 24 having a relatively lower hardness than diamond is abraded faster than the diamond particles 23, and as a result, as shown in FIG. 4, after using the cutting blade for a long period of time, the diamond particles 23 are exposed from the surface of the cutting segments 22. In the conventional cutting blades, however, the diamond particles 23 have no strong binding force with the sintered metal powder 24 in the cutting segments, and consequently tend to be easily fallen off from the surface of the cutting segments 22 due to a shock caused by a rapid contact with an object to be cut.
Of course, as shown in FIG. 4, on the trailing sides of the diamond particles 23 exposed from the surfaces of the cutting segments 22 rotating in the arrow direction, abrasion of the sintered metal powder 24 is more slowly progressed than on the front sides of the diamond particles, and as a result, residual powder layers 25 are formed on the trailing sides of the diamond particles 23, which are slightly higher than the powder layers on the front sides of the diamond particles, so that the diamond particles 23 can be held by virtue of those residual powder layers to a certain extent. Nevertheless, the inventor of the present invention has found that the diamond particles are fallen off from the surfaces of the cutting segments when they are exposed from the surfaces about {fraction (1/10)}-⅓ in their size. Consequently, the cutting efficiency is deteriorated, and the life cycle of the cutting blade is shortened.
It is, therefore, an object of the present invention to provide a method for manufacturing cutting blades within a short period of time and with low manufacturing cost, by reducing the manufacturing process.
It is another object of the present invention to provide an apparatus for manufacturing cutting blades requiring relatively small space for installation and capable of economically manufacturing cutting blades with a simple manufacturing process, by using not separate and independent manufacturing facilities but a single manufacturing facility.
It is still another object of the present invention to provide a cutting blade having uniform distribution of diamond particles in the sintered diamond-metal powder mixture of the cutting segments.
It is still another object of the present invention to provide a cutting blade, in which diamond particles exposed due to abrasion of the cutting segments as a result of a long time use are not easily fallen off from the cutting segments.
It is still another object of the present invention to provide cutting segments for a cutting blade having uniform distribution of diamond particles in the sintered diamond-metal powder mixture thereof.
It is still another object of the present invention to provide cutting segments for a cutting blade, from which diamond particles exposed due to abrasion as a result of a long time use are not easily fallen off.
According to an aspect of the present invention to achieve the above objects, there is provided a method for manufacturing cutting blades, each having a disk-shaped steel core with a predetermined thickness and a plurality of cutting segments made of a mixture of diamond particles and metal powder and fixedly attached to the periphery of the steel core at regular intervals, comprising the steps of: preparing a diamond-metal powder mixture by mixing diamond particles of a predetermined size with metal powder of a predetermined ingredient and size; supporting the steel core of the cutting blade under the lower portion of a forming die consisting of at least one vertically reciprocating upper punch and a lower die assembly having at least one forming pattern of a cross-sectional shape corresponding to the upper punch; forming the diamond-metal powder mixture into cutting segments of a predetermined shape by filling a predetermined amount of the mixture into the forming pattern of the forming die and pressing the mixture in the forming pattern; sintering the metal powder in the diamond-metal powder mixture of the cutting segments by heating the mixture while its forming in the forming pattern; and welding the cutting segments, by said heating, to the periphery of the steel core placed at the lower portion of the forming pattern of the lower die assembly.
Further, according to a preferred embodiment of the present invention, there is provided a method for manufacturing cutting blades, which performs concurrently the steps of forming the diamond-metal powder mixture into cutting segments by pressing the mixture filled in the forming pattern of the forming die, sintering the metal powder in the diamond-metal powder mixture of the cutting segments by heating the diamond-metal powder mixture, and welding the cutting segments, by heating, to a predetermined portion of the periphery of the disk-shaped steel core.
Still further, according to the present invention, there is provided a method for manufacturing cutting blades, comprising a step of welding a plurality of cutting segments in order throughout the periphery of the disk-shaped steel core by stepwise rotating the steel core at a predetermined angle.
In applying the method for manufacturing cutting blades of the present invention, preferably, the diamond-metal powder mixture is composed of metal powder of a predetermined ingredient and size and diamond-metal powder granules preformed by coating the metal powder of a predetermined ingredient and size around the diamond particles of a predetermined size.
According to another aspect of the present invention, there is provided an apparatus for manufacturing cutting blades, each having a disk-shaped steel core with a predetermined thickness and a plurality of cutting segments made of a mixture of diamond particles and metal powder and fixedly attached to the periphery of the steel core at regular intervals, comprising: at least one vertically reciprocating upper punch; a lower die assembly having at least one forming pattern of a cross-sectional shape corresponding to the upper punch for filling the mixture of the diamond particles and the metal powder therein and forming the mixture into a predetermine shape; and a supporting device for supporting the disk-shaped steel core having a predetermined periphery thereof positioned at the lower portion of the forming pattern of the lower die assembly.
Further, according to a preferred embodiment of the present invention, there is provided a manufacturing apparatus, further comprising heating means for heating the diamond-metal powder mixture filled into the forming pattern of the lower die assembly. Preferably, the heating means is electric heating means. More preferably, the heating means comprises an induction-heating coil arranged outside of the forming pattern of the lower die assembly.
Still further, according to the present invention, there is provided a manufacturing apparatus, further comprising at least one cooling or heat sink means arranged under the lower portion of the forming pattern of the lower die assembly so as to be in contact with both or any one of the side surfaces of the disk-shaped steel core placed under the lower portion of the forming pattern of the lower die assembly.
Still further, according to the present invention, there is provided a manufacturing apparatus, further comprising rotating means for stepwise rotating the disk-shaped steel core at a predetermined angle so as to weld a plurality of cutting segments in order throughout the periphery of the steel core.
In manufacturing cutting blades using the apparatus of the present invention, preferably, the diamond-metal powder mixture is composed of metal powder of a predetermined ingredient and size and diamond-metal powder granules preformed by coating the metal powder of a predetermined ingredient and size around the diamond particles of a predetermined size.
According to a further aspect of the present invention, there is provided a cutting blade having a disk-shaped steel core with a predetermined thickness and a plurality of cutting segments made of a mixture of diamond particles and metal powder by forming and sintering the mixture in a predetermined shape and fixedly attached to the periphery of the steel core at regular intervals, wherein the cutting segments are made of a mixture of metal powder of a predetermined ingredient and size and diamond-metal powder granules preformed by coating the metal powder of a predetermined ingredient and size around the diamond particles of a predetermined size.
According to a still further aspect of the present invention, there is provided cutting segments made of a mixture of metal powder of a predetermined ingredient and size and diamond-metal powder granules preformed by coating the metal powder of a predetermined ingredient and size around the diamond particles of a predetermined size, by forming and sintering the mixture in a predetermined shape.